Comets do not give off their own light but reflect light from other sources , such as the Sun.Scientists estimate the mass of comets by their brightness: the greater a comet's mass, the more light that comet will reflect. A satellite probe, however, has revealed that the material of which Halley's comet is composed reflects 60 times less light per unit mass than had been previously thought.
(A) Some comets are composed of material that reflects 60 times more light per unit of mass than the material of which Halley's comet is composed.
Not necessary right, there is no comparison that could be drown by the argument between Halley's comet and other comets.
(B)Previous estimates of the mass of Halley's comet which were based on its brightness were too low.
It is the opposite, the estimate was higher then what had been revealed.
(C) The total amount of light reflected from Halley's comet is less than scientists had previously thought.
This is my choice because it could be implied by the bold part of the argument
(D) The reflective properties of the material of which comets are composed vary considerably from comet to comet.
Could not be supported by the argument above.
(E) Scientists need more information before they can make a good estimate of the mass of Halley's comet.
Why they have to do so? Not supported.
I hope this will help.
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